CsPbI2Br perovskite solar cells (PSCs) based on carbon
electrodes (CEs) are considered to be low-cost and thermally stable
devices. Nevertheless, the insufficient contact and energy level mismatch
between the CsPbI2Br layer and CE hinder the further enhancement
of the cell efficiency. Herein, a carbon black (CB) interlayer was
introduced between the perovskite layer and CE. The hole extraction
was facilitated due to the larger contact area and suitable energy
band alignment in the CsPbI2Br/CB interface. Further investigation
indicated the diffusion of CB nanoparticles from the CE or CB layer
to the CsPbI2Br film after a certain period of time. We
disclosed the formation of a CB-CsPbI2Br bulk heterojunction
structure due to the carbon diffusion, which resulted in an efficiency
enhancement. As a result, a record efficiency of 13.13% is achieved
for carbon-based inorganic PSCs. This work also reveals that the diffusion
of CB nanoparticles in CB-containing PSCs is universal and inevitable,
although this kind of diffusion results in the enhancement of cell
efficiency.
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